Dredging - Lowe Bure - Lack Of Maintenance

[Paladin]

On 05/12/2023 at 05:49, grendel said:

I tried to get the depth surveys for previous years to compare to the current ones but could not find them, I would be interested in looking at the various surveys and comparing them over the last 30 or 40 years to see if the depths have changed.

The earliest document that may have some relevance that I have been able to find is from 2008. See attached.

It clearly shows that the Bure Loop is a substantial bottle-neck, being as shallow as the upper reaches of the system. This is something the Broads Authority have acknowledged in the past.

It wouldn't matter so much if the only source of water in the Broads was from the sea. The loop would restrict the flow in and out by the same amount. But add rainfall, run off from the land, input from sewage treatment works, output of grey water from boats, etc., and it's obvious that more water enters the Broads than leaves it. There is a cumulative effect and over a long period of time, that will have the effect, on the Northern Broads, of raising the river levels.

I've looked at the changes in bridge heights over the years. Those below the loop, and on the Southern Broads are unchanged. The airdraft of the Northern bridges has decreased.

[report] Sediment Management Strategy draft ActionPlan nc240408.doc

[webntweb]

On 04/12/2023 at 22:36, marshman said:

It takes some stretch of the imagination to see at least 8' under Wroxham even in the early '80's - others clearly think otherwise but i never remember it being anything like that in my memory back to the mid 60's.

Pic attached is August 85. Definitely showing at least 8ft and I seem to recollect that a rise and fall of 3 to 4 inches was the norm.

[Vaughan]

1 hour ago, Paladin said:

It clearly shows that the Bure Loop is a substantial bottle-neck, being as shallow as the upper reaches of the system. This is something the Broads Authority have acknowledged in the past.

Very interesting and thank you for finding it. I got a bit lost in all the jargon from about half way through.

The map in section 6.1 shows that the whole of the navigable river Ant is significantly deeper than the Bure loop!

[dom]

The Ordnance Survey guide to the Broads and Fens : River Ouse, River Nene, Middle level navigations (1986)

[Bikertov]

1 hour ago, Paladin said:

The earliest document that may have some relevance that I have been able to find is from 2008. See attached.

 

 

From point 7.2 on page 7 !

Quote

The accelerated implementation of the dredging programme shows that the backlog could be cleared in 39 years, by 2047

and that was back in 2008, assuming work would progress in the meantime at the given rate

[dom]

16 minutes ago, Bikertov said:

and that was back in 2008, assuming work would progress in the meantime at the given rate

Playing devil's advocate, that was based in part on 06-07 performance. I think it was probably 07 when BA took on May Gurney's dredging operations, so following years may have seen an improvement.

Obviously, equally possible it got worse!

One thing I noticed is that page 5 refers to depths at Mean Low Water springs. Recent documents seem to just refer to MLW. Obviously the two mean different things. If someone had copied over an old specification and omitted that one word somewhere down the line, it could mean thousands, if not millions of tonnes less material being removed across the system.

[Vaughan]

1 hour ago, dom said:

One thing I noticed is that page 5 refers to depths at Mean Low Water springs. Recent documents seem to just refer to MLW. Obviously the two mean different things.

Quite agree!

MLWS is an international standard laid down by the Hydrographer of The Navy on Admirality charts, worldwide.

As such, it is one of the oldest standards that exist.

 

[Roy]

Looking through a lot of old broads hire boat magazines lots of boats say they’ll pass under wroxham many that wouldn’t pass under there today. 

[Broads01]

8 hours ago, webntweb said:

Pic attached is August 85. Definitely showing at least 8ft and I seem to recollect that a rise and fall of 3 to 4 inches was the norm.

How times change, especially as I recall that was a particularly wet summer. Just look at the amount of clearance that Bounty had.

[rightsaidfred]

I think we would all accept that water levels are higher now, I also think we accept that a comprehensive dredging regime is necessary and overdue to protect the integrity of the system particularly the lower reaches, what I am not sure of is whether dredging in itself will benefit water levels.

It has become quite noticeable in recent years that winds have increased considerably in both quantity and strength, alongside this there has been an increase in both the number of times and length of time that we have has salt surges and tidal locking neither of which we have any control over, I have noticed more and more the number of times on the Northern system that there has been no ebb tide between two highs, this is particularly noticeable at PH and Horning but applies everywhere, it has also been noticeable how much more unpredictable the tides have become due to prevailing conditions, the flooding of fields is more to do with the water table and rainfall than river levels as the amount of flooded fields etc. is quite noticeable driving around many areas away from both rivers and Norfolk.

Not being an engineer or any other sort of expert I can only rely on observation and logic to see potential problems with any sort of barrier in GY, first water has to go somewhere if you restrict the Bure it will push more onto and across Breydon into the Southern rivers, there is also the problem that the flood tide starts while the Bure is still ebbing so when exactly do you raise a barrier without impeding the last hour or so of the ebb, added to which how do you prevent it interfering with navigation as that is all around the time boats want to cross Breydon.

Personally I have never and still don't believe that any amount of the tinkering we are doing will alter the natural climate evolution we are seeing until the planets cycle reaches its peak, better we stop building in areas that are inappropriate and concentrate on achieving a sustainable population instead.

Fred      

[Bytheriver]

On 03/12/2023 at 14:08, BroadAmbition said:

Bytheriver - You make a fair point - BUT - if the Blessed Authority had kept the Lower Bure clear for navigation to the same state it was in when they inherited it when they were formed - It naturally follows on that drainage wouldn't be restricted to the state and levels we see nowadays

 

All went in re-structuring & are now hired when needed.

I could make a very easy argument that they are needed right now and for the foreseeable 

Griff

But not from the Navigation budget surely - It could take the whole budget.

 

[Bytheriver]

No doubt you have all seen this from Environment Agency?

River Thurne flooding November 2023.pdf

[Vaughan]

18 minutes ago, Bytheriver said:

No doubt you have all seen this from Environment Agency?

No I hadn't : thank you for posting.

I cringed when the very first paragraph said that the EA was "working collaboratively with partner organisations".  According to the press and TV articles I have seen, they and their "partners" are all denying responsibility and blaming each other!

I do notice that on two occasions they mention the need for what I have always known as "washlands" but which they call "deliberate overtopping".  At least they acknowledge it is necessary but fail to mention that there is nowhere near as much of this washland since their own flood banks (lobbied by the farmers) prevented this from happening.

I still refuse to believe that river dredging would not relieve this present form of alluvial (rainwater) flooding.

I get the overall impression that their attitude is just "Keep calm and carry on".  Is this good enough?

 

[grendel]

A thought has struck me, we keep sayiing the water levels have risen- but the depth of the water has got less, surely this is evidence that the rivers are being allowed to silt up, because if the rivers havent silted up and the water levels are higher, then the depths should be greater now, than they were before, eg if there was 6 feet depth and the water level has risen 6" there should be 6'6" depth, instead we are seeing 5' depth, so the river bottom has come up 18" while the water rose 6". so this may be why the surveys dont show much change, because while the rivers have been silting up, the water levels have also risen.

[BroadAmbition]

That Grendel is a really good and fair point. I’m gonna put it on the Brag group

Why didn’t I think of I?

Griff

[rightsaidfred]

4 hours ago, Bytheriver said:

No doubt you have all seen this from Environment Agency?

River Thurne flooding November 2023.pdf 147.12 kB · 24 downloads

Another example of PR departments stating the obvious and telling us what we already know.

Fred

[Bytheriver]

4 hours ago, Bytheriver said:

But not from the Navigation budget surely - It could take the whole budget.

 

That is no doubt why EA are responsible for dredging for drainage purposes. Broadland Futures Initiative ( poorly named as it covers far more than the Broadland District Council area) led by EA though website hosted by BA has a lot of information plus the January edition of Harnser has a brand new update in the January edition They seem finally to be making some progress

 

[marshman]

I believe all dredging on the Broads, has to be approved by and in conjunction with, the EA. I may be wrong - not unusual as Griff will confirm!!!!

[dom]

I'd imagine Natural England probably have a say somewhere down the line?

BA's original formation was monitored and audited by the Countryside Commission. I believe they've now effectively evolved into Natural England.

[Bikertov]

41 minutes ago, marshman said:

I believe all dredging on the Broads, has to be approved by and in conjunction with, the EA. I may be wrong - not unusual as Griff will confirm!!!!

Just want to clarify ... Is that the dredging of the Broads by the EA that is not unusual, or you being wrong that is not unusual ?

 

[grendel]

or that you may be wrong but you are not unusual?

[marshman]

All of them i guess!!!

[MargeandParge]

6 hours ago, grendel said:

A thought has struck me, we keep sayiing the water levels have risen- but the depth of the water has got less, surely this is evidence that the rivers are being allowed to silt up, because if the rivers havent silted up and the water levels are higher, then the depths should be greater now, than they were before, eg if there was 6 feet depth and the water level has risen 6" there should be 6'6" depth, instead we are seeing 5' depth, so the river bottom has come up 18" while the water rose 6". so this may be why the surveys dont show much change, because while the rivers have been silting up, the water levels have also risen.

That is why I asked about the Gorleston bar. I honestly have know idea.

Kindest Regards Marge and Parge 

[BroadAmbition]

Bytheriver

But not from the Navigation budget surely - It could take the whole budget.

And then some I fear.  The Blessed Authority is the maker of its own problem here.  Imho with regards to the Lower Bure - if they had just maintained what they inherited then three points  1) We wouldn't be in the situation we currently find the Northern broads.  2) They wouldn't be in a position of realistically not being able to afford to put it right financially or have the plant to do it on such a large scale that is now needed  3) We may, just may be holding them in a slightly better light

Griff

[BroadAmbition]

Marshman

I believe all dredging on the Broads, has to be approved by and in conjunction with, the EA. I may be wrong - not unusual as Griff will confirm!!!!

I cannot confirm or deny - but I would tend to agree with you.  However assuming you are correct - would the EA really not approve of the BA dredging the lower Bure to maintain navigation?  I would hope not

Griff